1. Technical Field
The present disclosure relates to cannula assemblies which are adapted to allow the introduction of a surgical instrument into a patient's body. In particular, the disclosure relates to cannula assemblies having a cannula configured to be shortenable from a first length to a second length.
2. Background of Related Art
Laparoscopic procedures are performed in the interior of the abdomen through a small incision, e.g., through narrow endoscopic tubes or cannulas inserted through a small entrance incision in the skin. Minimally invasive procedures performed elsewhere in the body, e.g., in the chest, are often generally referred to as "endoscopic" procedures. Minimally invasive or endoscopic procedures generally require that any instrumentation inserted into the body be sealed, i.e. provisions must be made to ensure that gases do not enter or exit the body through the endoscopic incision as, for example, in surgical procedures in which the surgical region is insufflated. Moreover, endoscopic procedures often require the surgeon to act on organs, tissues, and vessels far removed from the incision, thereby requiring that any instruments used in such procedures be relatively long and narrow.
For such procedures, the introduction of a tube into certain anatomical cavities such as the abdominal cavity is usually accomplished by use of a system incorporating a trocar and cannula assembly. A cannula assembly is formed of a cannula attached to a cannula housing which generally includes a valve assembly adapted to maintain a seal across the opening of the valve assembly both with and without an instrument inserted therethrough. Since the cannula is in direct communication with the internal portion of the valve assembly, insertion of the cannula into an opening in the patient's body so as to reach the inner abdominal cavity should be adapted to maintain a fluid tight interface between the abdominal cavity and the outside atmosphere.
Since minimally invasive surgical procedures in the abdominal cavity of the body generally require insufflating gases to raise the cavity wall away from vital organs, the procedure is usually initiated by use of a Verres needle through which a gas is introduced into the body cavity. The gas provides a slight pressure which raises the wall surface of the peritoneum away from the vital organs thereby providing an adequate region in which to operate. Thereafter, a trocar assembly which includes a trocar or obturator is inserted within the cannula to puncture the peritoneum, i.e. the inner lining of the abdominal cavity wall. The obturator is removed and laparoscopic or endoscopic surgical instruments may then be inserted through the cannula to perform surgery within the abdominal cavity. The cannula may also be utilized for introducing tubes into the body as for drainage purposes, for specimen removal, for diagnostic evaluations, or the like.
In view of the need to maintain the atmospheric integrity of the inner area of the cavity, a valve assembly for a cannula which permits introduction of an obturator and a wide range of surgical instruments and which maintains the atmospheric integrity of the inner area of the cavity is desirable. A particularly suitable valve assembly is disclosed in commonly-assigned, copending U.S. patent application Ser. No. 08/287,395, filed Aug. 8, 1994 by Smith et al., the contents of which are hereby incorporated by reference. This valve assembly is capable of forming and maintaining a tight seal about instruments of varying diameters inserted through the cannula and incorporates structure to enhance and facilitate passage of the instrument through the valve unit.
In addition, it is also desirable to maintain the position of the cannula assembly within the body tissue during the surgical procedure. In particular, the position of the cannula assembly may be disturbed by the insertion and removal of surgical instrumentation, as well as the manipulation thereof within the body cavity.
U.S. Pat. No. 5,002,557 to Hasson, for example, suggests a cannula assembly having a sleeve which may be inserted into a body cavity. The sleeve includes expandable structure at a distal end thereof to prevent withdrawal of the sleeve. A retaining collar is movable relative to the sleeve to capture tissue between the collar and the expandable structure to maintain the sleeve in position.
U.S. Pat. No. 5,290,249 to Foster et al. disclose a retention mechanism for a cannula assembly inserted through the abdominal wall. A plurality of laterally expanding retention strips engage the interior surface of the abdominal wall, and a retention dish engages the external surface of the abdominal wall in order to stabilize the cannula assembly.
A limitation of known cannula assemblies concerns the substantial length of the cannula. The length of the cannula is generally selected to span a range of anatomies and may, in certain instances, be influenced by the retention mechanism which may be slidably mounted on the cannula to positively secure the cannula to body tissue. Consequently, the portion of the cannula assembly which extends above the body cavity may be greater than otherwise desired.
A need exists, therefore, for a cannula assembly which facilitates introduction of instruments to a surgical site, while minimizing the profile of the cannula assembly above the body wall to the extent possible.